From Halopedia, the Halo wiki
Universe and lore
The map is set in an area similar to the outside of Dr. Halsey's lab from the level The Package, also known as Glacier. According to the 12/02/10 Bungie podcast, it is the Side B to the Side A that is the firefight map, Glacier. During Invasion, the game goes from the Front yard where the Research center is located, to the Back yard where the Vault is located. The Spartans will spawn in the Research Center and the Elites will spawn in the cliff area. When the Elites take over the two territories in the first phase, the Bridge will come down and the Tunnel will open to give access to the Back Yard. The Elites must then plant a bomb on the outside of the vault to gain access to the core. When the walls of the Vault are blown open, the Elites must take the core to the Phantom located near the Bridge. The map is also compatible with the Race gametype.
The following are locations on the map that are so named on the player's heads-up display during gameplay: